AstraZeneca surprised the City today as it raised its sales and earnings forecast for the year, bolstering its case for a strong future as an independent company after rejecting a £69billion approach from US rival Pfizer earlier this year.

The UK drugmaker, which was recently boosted by successful trials of new cancer drugs, said sales in the quarter rose 4 per cent to $6.45billion, better than analysts’ forecast for $6.29billion.

Strong demand of its Symbicort respiratory drug in the US and a doubling of sales for its new diabetes medicines, as well as several one-off payments, were behind the improved performance, according to the firm.

New drugs in the pipeline: Staff working in AstraZeneca's labs in Cambridge

AstraZeneca said it now expected full year revenues to be in line with last year, rather than declining as previously stated, and profits to fall by less than previouslyforecasted.

Shares in the company, which have risen by a third in the past 12 months, were down 34.25p at 4,323.25p in mid morning trading.

Viagra maker Pfizer approached AstraZeneca two months ago, but the British drug maker rebuffed its offer calling it insubstantial.

Pfizer, like other American firms, is looking to acquire a British firm in a bid to slash its international tax bill and give it access to cutting-edge research.

But since the deal collapsed, Astra chief executive Pascal Soriot has been keen to demonstrate that the company has a strong future as an independent drugmaker.

AstraZeneca yesterday announced a £1.2billion deal to buy the rights to respiratory drugs from Spanish group Almirall.

Under the deal Astra is allowed to sell and develop Almirall’s existing respiratory treatments, as well as its new pipeline. A ‘significant’ number of employees will also transfer to Astra.

Astra paid $1.15billion last month for Californian firm Pearl Therapeutics, which also increases its capabilities in the area of respiratory treatments. It has also signed a cancer trial collaboration with Japan’s Kyowa Hakko.

‘The pace of execution of our strategy and the underlying performance of our teams give us confidence to raise 2014 guidance for the full year,’ Soriot said in a statement. ‘We now have one of the most exciting pipelines in the industry.’

He also said: ‘The business combination with Almirall will offer strategic long-term value, bringing together the two innovative portfolios to strengthen further our commitment to respiratory disease and contribute to our growth.’

Deutsche Bank analyst Mark Clark said today's results represented a ‘big beat’ but were flattered by one-time items and the increased outlook for the year was likely to be taken in its stride by the market.

AstraZeneca was boosted by a $200million payment from Pfizer for launching an over-the-counter version of heartburn pill Nexium in May and by an $80million payment related to the Japanese launch of diabetes drug Forxiga.

It also received $117million from an inter-governmental agreement on a transfer pricing matter, which cut its tax rate in the period sharply.

Many investors believe Pfizer is likely to launch a second attempt to buy AstraZeneca despite itself reporting a poor set of financial figures earlier this week, with profits down 25 per cent in the first half of the year and no new drugs in the pipeline.

Astra rebuffed Pfizer's final offer May, so now the US company has to wait until November before it can make another unsolicited approach.